This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Photosynthesis is a central biological process that produces all the food and much of the energy used by human beings. An enormous amount of work has been done to understand the structural basis of light harvesting and the efficiency of the energy-transfer process. Several bacterial light-harvesting (LH) complexes, such as LH1, LH2 and Fenna-Matthews-Olson protein (FMO) have served as model systems for structural, spectroscopic and theoretical studies.. The recently discovered, thermophilic bacterium, Candidatus Chloracidobacterium (C.) thermophilum, belongs to the phylum Acidobacteria, and is the only chlorophototroph found in the phylum so far. Surprisingly, the photosystem of the aerobic C. thermophilum closely resembles that of the green sulfur bacteria (GSB), which are strict anaerobes. However, The mechanism that enables the C. thermophilum cells to carry out phototrophy under aerobic conditions is not yet known. FMO proteins of green sulfur bacteria (Chlorobiales) have been extensively studied using a wide range of spectroscopic and theoretical approaches. The new FMO protein is investigated by several approaches including native electrospray in a Bruker 12 tesla FTICR mass spectrometer.